There have been known in the art such assistive music playing apparatuses that convert roughly played music input signals to proper music playing signals in view of music theory or grammar, so that even a player having poor musical skill and knowledge can enjoy playing music without giving precise care to music theory and grammar. (For example, see unexamined Japanese patent publication No. 1993-27757.)
With a conventional assistive music playing apparatus, however, the inputted music playing signals (i.e. played notes) are uniformly converted to the chord constituent notes or to the scale notes of the designated tonality (key), and may not necessarily make the most of the player's feeling.
Another type of assistive music playing apparatus has been introduced in the art, which apparatus plays back some accompaniment or some music data along with a chord progression and permits the player to play music over such an accompaniment by manipulating the music playing controls such as keys on a keyboard. (For example, see unexamined Japanese patent publication No. 1993-188956.) With such an apparatus, the user may manipulate a key or keys causing generation of a note or notes which may not go well with the concurrently generated accompaniment tones.
A further conceivable method is a method in which the notes played by the user are converted under a prescribed rule to the constituent notes of previously set chords, which method may bring forth a situation where a converted note coincides with another note which is already being generated concurrently. If such coincident notes are generated without care, there may arise a phenomenon of “flanging” (a phenomenon caused by interference of two waveforms, when the pitches, the phases and timbre are very close to each other) resulting in tones quite different from the source or original tones. Further, in the very low frequency range, even though the pitches of two tones are not the same or very close, but if the pitches of two tones are close to some extent, simultaneous sounding of two tones will cause unclear mumbling, thus deteriorating the naturalness of sounds in the acoustic field.
Where the above-mentioned conversion method is employed to convert the user-played notes to the notes which agree with the chord constituent notes under a predetermined rule, no notes other than the chord constituent notes would be generated, even though the user might depress the keys in a manner which would typically cause the generation of notes other than the chord constituent notes, for example by intentionally depressing close black keys or ten keys simultaneously. Such a situation will not be a nuisance from an ordinary point of view in music performance, but will be monotonous and non-surprising with only chord tones to realize a stable music performance.
Further, the above-mentioned conversion method will not cause different conversions for different timbres (voices), or cause conversion to unexpected note pitches which should not be generated normally, or cause conversion to more notes than the number of simultaneously available notes, depending on timbres (voices).